Method and apparatus for forming a foundation-leg assembly for an offshore platform

ABSTRACT

A pile is driven through a first formation and into a subterranean second formation of the earth beneath a body of water, a cavity is formed below the pile and extends outwardly beyond the pile, and a concrete volume is thereafter formed in the cavity and a portion of the pile. The pile is in intimate contact with the first and second formations and the concrete is in intimate sealing contact with the pile and the second formation.

United States Patent Bowles [54] METHOD AND APPARATUS FOR FORMING A FOUNDATION-LEG ASSEMBLY FOR AN OFFSHORE PLATFORM [72] Inventor: William R. Bowles, Bartlesville, Okla.

[73] Assignee: Phillips Petroleum Company [22] Filed: Jan. 7, 1971 [21] Appl. No.: 104,606

[52] US. Cl. ..61/46, 61/52, 61/536, 61/53.64

[51] Int. Cl. ..E02d 5/40, E02d 5/44, E02d 27/32 [58] Field ol'Search ..61/46, 53.6, 53.64, 53.5, 52, 61/50, 53.66

[56] References Cited UNITED STATES PATENTS 1,751,607 3/1930 Smith ..61/53.6

[15] 3,677,113 1 July 18, 1972 Primary Examiner-Jacob Shapiro Attorney-Young and Quigg ABSTRACT A pile is driven through a first formation and into a subterranean second formation of the earth beneatha body of water. a cavity is formed below the pile and extends outwardly beyond the pile, and a concrete volume is thereafter formed in the cavity and a portion of the pile. The pile is in intimate contact with the first and second formations and the concrete is in intimate sealing contact with the pile and the second formation.

13 Claims, 1 Drawing Figure PATENIED Jun 8 m2 INVENTOR.

W. R. BOWLES A TTORNEYS METHOD AND APPARATUS FOR FORMING A FOUNDATION-LEG ASSEMBLY FOR AN OFFSHORE PLATFORM In the construction of offshore foundations and platform legs for offshore platforms that are utilized for drilling or production, for example, a barge is utilized. Owing to the adverse, violent weather conditions, particularly where said platform is being erected in the North Sea area, the construction barge is often able to perform its assigned construction tasks for average periods of only 12 hours or less during each 24 hours. Regardless of the construction progress, it is a general policy that rental fees for the barge and its associated equipment continue during the bad weather conditions, irrespective of the idle time encountered.

It is therefore an object of this invention to provide a method for forming a unique foundation and leg of an offshore platform.

This invention therefore resides in driving a pile through a first formation and into a second formation beneath a body of water, fonning a cavity beneath the pile which has at least a portion thereof extending laterally through the second fonnation a radial distance beyond the pile, and forming a reinforced concrete volume within the cavity and a portion of the pile with the pile in intimate contact with the formation and the concrete in intimate sealing contact with the pile and the second formation.

Other aspects, objects, and advantages of the present invention will become apparent from a study of the disclosure, the appended claims, and the drawing.

The drawing is a diagrammatic view in partial section of the body of water, pile, jacket, concrete and reinforcing member of the method and apparatus of this invention.

Referring to the drawing, a body of water 2 overlies a first fonnation 4 of the earth which in turn overlies a second formation 6. The body of water 2 is generally considered to be sea water such as that of the North Sea area, but can be any body of water. The first formation can be formed of a plurality of different geological formations but the term as herein utilized refers to the portion of the earth underlying the body of water that is relatively less dense and consolidated that the second formation 6. That first formation 4 is, for example, mud, silt, sand, thin shale stringers, and like material through which pilings can be relatively easily inserted. The term second formation as used herein, refers to relatively more dense and consolidated formations through which piling is relatively more difficult to install therethrough by pile driving methods and which material is of sufficient strength to withstand relatively heavy loading in both tension and com pression. That second formation 6 is, for example, dense shale.

The metal pile 8 is driven by pile driving equipment known in the art through the first formation 4 and into the second formation 6. The pile has a chamber 9 extending therethrough and an outer surface 10 that, in the installed position, is in intimate contact with the first and second formations 4,6. In said installed position, the pile 8 extends from a location above the body of water 2, through the body of water 2, through the first formation 4, and a preselected distance into the second formation 6. A lower end 12 of the pile 8 is preferably at a location at least about 10 feet below an upper surface 14 of the second formation in order to assure sufficient overburden of the second formation to provide sufficient strength to withstand tension and compressive forces exerted on the second formation by the assembly. In order to further assure an assembly of sufficient anchorage to the formation, it is also preferred that, in the installed position, the lower end 12 of the pile 8 be at an elevation at least 90 feet below the overlying body of water 2.

A cavity 16 is formed within the second formation 6 at a lower elevation than the pile 8. The cavity 16 extends downwardly from the pile 8 a preselected distance and at least a portion of the cavity 16 extends laterally, outwardly from the pile a preselected radial distance beyond the outer surface 10 of the pile 8. The depth and radius of the cavity 16 are distances that depend upon factors such as the tension and compressive loads expected to be exerted on the foundationleg assembly and the denseness and consolidation of the second formation and are distances that earn be easily selected by one skilled in the art.

At least one metal reinforcing member 17, preferably a plurality of members, can be installed within the cavity 16 with said member 17 preferably extending from within a second portion 18 of the cavity 16, upwardly through the cavity 16 and into the pile 8 and terminating at an elevation at least higher than the upper surface 14 of the second formation 6 and, preferably, to assure an assembly of greater stability, at an elevation about halfway between the upper surface 14 of the second formation 6 and the body of water 2.

A volume of concrete 20 or cement is positioned within the cavity 16 and pile 8. It is preferred that the reinforcing member 17 be maintained in axial alignment with the pile 8 until the concrete 20 sets to assure a more even distribution of stress. In the set condition, the volume of concrete has a first end 22 within the pile at an elevation at least above the second formation 6, a second end 24 at a location spaced a preselected distance downwardly from the lower end 12 of the pile 8 contiguous with the cavity 16, a first portion 26 within the pile, and a second portion 28 within the cavity 16 with at least a portion of the second portion 28 of the concrete volume 20 extending laterally and outwardly from the pile 8 a preselected radial distance beyond the pile 8. In the set condition, the first and second portions 26, 28 of the concrete are in intimate sealing contact with their respective pile 8 and I second formation 6.

In order to provide an assembly of greater stability, it is preferred that the first end 22 of the concrete be positioned at an elevation higher than the subterranean first formation 4.

One example of the cavity 16 and reinforced concrete volume 20 that will provide an excellent foundation-leg assembly for an offshore platform in the North Sea area is a cavity l6 and concrete member that has a second end 24'located a distance of at least ll feet downwardly from the lower end 12 of the pile and extends a radial distance of at least 4.25 feet laterally, outwardly beyond the outer surface 10 of the pile 8. In this example assembly, the pile 8 is constructed of steel pipe having an outside diameter of about 42 inches and a wall thickness of about 1 1% inch and the reinforcing member 17 is a steel rod, preferably a plurality of rods. The member 17 terminates at a location about median the first formation 4 and has an outwardly extending protrusion affixed at its lower end.

A metal jacket 30 can be about the pile and extend from a location above the body of water, through the body of water and into the first formation 4. That jacket can be a separate member or be a portion of a platform assembly that is connected to and bears against the foundation leg assembly of this invention.

In the method of this invention, the pile 8 having a chamber 9 extending therethrough is driven by a pile driving means known in the art through the first formation 4 and a preselected distance into the second formation 6. The pile can be driven through the jacket assembly from an overlying platform.

The portions of the first and second formations 4,6 within the chamber 9 of the pile in the set position of the pile are thereafter removed by bailing, drilling, reverse circulating, or

other means known in the art. The cavity 16 in the second formation 6 below the lower end 12 of the pile 8 is then formed by means known in the art such as, for example, jet drilling, shooting the formation, bailing, etc. The reinforcing member 17 is thereafter installed and the concrete 20 is installed by means known in the art such as, for example, running a conduit to a position adjacent the bottom of the cavity and pumping concrete into the cavity and upwardly through the pile 8. Care should be taken, however, in forming the cavity and spotting the concrete not to create forces sufficiently large to destroy the intimate contact between the pile 8 and the formations 4,6.

The foundation-leg assembly of this invention is of a construction which requires the penetration of the pile to lesser depths than heretofore employed assemblies, thereby reducing the time and labor construction requirements. The intimate contact of the pile with the formation provides a great deal of force to counteract tension and/or compression loading on the pile from the platform connected thereto. By providing a concrete pier as footing for the pile by the method of this invention, the downward and upward directed loads exerted on the pile are distributed over a substantially greater area of the formation thereby permitting the pile to be securely anchored to the formation at more shallow depths than heretofore utilized.

Other modifications and alterations of this invention will become apparent to those skilled in the art from the foregoing discussion, example, and accompanying drawing, and it should be understood that this invention is not to be unduly limited thereto.

What is claimed is:

l. A method for forming a foundation and leg of an offshore platform, comprising:

driving a pile having a chamber downwardly through a first formation and a preselected distance into an adjacent second formation of the earth positioned beneath said first formation, said first and second formations being positioned beneath the surface of a body of water and said second formation being substantially more dense and consolidated than said first formation;

removing the portions of first and second formations within the chamber of the pile;

removing a portion of the second formation through the pile for forming a cavity in the second formation at a lower elevation than the pile, said cavity extending downwardly from the pile a preselected distance and at least a portion of the cavity extending laterally, outwardly from the pile a preselected radial distance beyond said pile;

filling the cavity and filling at least a portion of the length of the chamber of the pile with concrete, said concrete filled portion of the pile extending from the cavity upwardly to an elevation at least higher than an upper surface of the second formation; and

maintaining the pile in contact with the first and second formations and the concrete in contact with the second formation and the pile chamber for a time suflicient for the concrete to set.

2. A method, as set forth in claim 1, including driving the pile into the second formation a distance of at least l feet.

3. A method, as set forth in claim 1, including driving the pile through the first and into the second formation to an elevation spaced at least 90 feet below the body of water.

4. A method, as set forth in claim 1, including removing a sufficient portion of the second formation for forming a cavity therein extending downwardly from the pile a distance of at least about 1 l feet and with at least a portion of the cavity extending a radial distance of at least about 4.25 feet laterally, outwardly beyond said pile.

5. A method, as set forth in claim 1, including filling the cavity and at least a portion of the chamber of the pile with an amount of concrete sufficient to position an upper surface of the concrete at an elevation higher than the subterranean first formation.

6. A method, as set forth in claim 1, including driving the piling through a jacket extending from an elevation above the body of water, through the body of water and into contact with the first formation.

7. A formation and leg assembly of an offshore platform, comprising:

a metal pile having an outer surface, a lower end, and a chamber, said pile extending from a location above the surface of a body of water, through the body of water, through an adjacent subterranean first formation positioned beneath said first formation and a preselected distance into substantially more dense subterranean second formation with the outer surface of said pile being in intimate contact with the first and second formations; and

a volume of concrete having first and second ends and first and second portions, said first end being within the pile at an elevation at least above the second formation, said second end being at a location spaced a preselected distance downwardly from the lower end of the pile, the first portion filling and being within the pile chamber, and at least a portion of said second portion extending laterally outwardly through the second formation from the pile a preselected radial distance beyond said pile with said first and second portions being set and in intimate sealing contact with their respective pile and second formation.

8. An assembly, as set forth in claim 7, wherein the lower end of the pile is positioned in the second formation at a distance of at least 10 feet below an upper surface of the second formation.

9. An assembly, as set forth in claim 7, wherein the lower end of the pile is positioned within the second formation at an elevation of at least feet below the overlying body of water.

10. An assembly, as set forth in claim 7, wherein the second end of the volume of concrete is located a distance of at least 1 1 feet downwardly from the lower end of the pile and with at least a portion of the second end portion of the volume of cement extending a radial distance of at least 4.25 feet laterally, outwardly beyond said pile.

11. An assembly, as set forth in claim 7, wherein the first end of the concrete is at an elevation higher than the subterranean first formation.

12. An assembly, as set forth in claim 7, wherein the pile is a metal conduit having an outside diameter of about 42 inches and a wall thickness of about 1 inches.

13. An assembly, as set forth in claim 7, including a metal jacket positioned about the pile and extending from a location above the body of water, through the body of water and into contact with the first formation. 

1. A method for forming a foundation and leg of an offshore platform, comprising: driving a pile having a chamber downwardly through a first formation and a preselected distance into an adjacent second formation of the earth positioned beneath said first formation, said first and second formations being positioned beneath the surface of a body of water and said second formation being substantially more dense and consolidated than said first formation; removing the portions of first and second formations within the chamber of the pile; removing a portion of the second formation through the pile for forming a cavity in the second formation at a lower elevation than the pile, said cavity extending downwardly from the pile a preselected distance and at least a portion of the cavity extending laterally, outwardly from the pile a preselected radial distance beyond said pile; filling the cavity and filling at least a portion of the length of the chamber of the pile with concrete, said concrete filled portion of the pile extending from the cavity upwardly to an elevation at least higher than an upper surface of the second formation; and maintaining the pile in contact with the first and second formations and the concrete in contact with the second formation and the pile chamber for a time sufficient for the concrete to set.
 2. A method, as set forth in claim 1, including driving the pile into the second formation a distance of at least 10 feet.
 3. A method, as set forth in claim 1, including driving the pile through the fIrst and into the second formation to an elevation spaced at least 90 feet below the body of water.
 4. A method, as set forth in claim 1, including removing a sufficient portion of the second formation for forming a cavity therein extending downwardly from the pile a distance of at least about 11 feet and with at least a portion of the cavity extending a radial distance of at least about 4.25 feet laterally, outwardly beyond said pile.
 5. A method, as set forth in claim 1, including filling the cavity and at least a portion of the chamber of the pile with an amount of concrete sufficient to position an upper surface of the concrete at an elevation higher than the subterranean first formation.
 6. A method, as set forth in claim 1, including driving the piling through a jacket extending from an elevation above the body of water, through the body of water and into contact with the first formation.
 7. A formation and leg assembly of an offshore platform, comprising: a metal pile having an outer surface, a lower end, and a chamber, said pile extending from a location above the surface of a body of water, through the body of water, through an adjacent subterranean first formation positioned beneath said first formation and a preselected distance into substantially more dense subterranean second formation with the outer surface of said pile being in intimate contact with the first and second formations; and a volume of concrete having first and second ends and first and second portions, said first end being within the pile at an elevation at least above the second formation, said second end being at a location spaced a preselected distance downwardly from the lower end of the pile, the first portion filling and being within the pile chamber, and at least a portion of said second portion extending laterally outwardly through the second formation from the pile a preselected radial distance beyond said pile with said first and second portions being set and in intimate sealing contact with their respective pile and second formation.
 8. An assembly, as set forth in claim 7, wherein the lower end of the pile is positioned in the second formation at a distance of at least 10 feet below an upper surface of the second formation.
 9. An assembly, as set forth in claim 7, wherein the lower end of the pile is positioned within the second formation at an elevation of at least 90 feet below the overlying body of water.
 10. An assembly, as set forth in claim 7, wherein the second end of the volume of concrete is located a distance of at least 11 feet downwardly from the lower end of the pile and with at least a portion of the second end portion of the volume of cement extending a radial distance of at least 4.25 feet laterally, outwardly beyond said pile.
 11. An assembly, as set forth in claim 7, wherein the first end of the concrete is at an elevation higher than the subterranean first formation.
 12. An assembly, as set forth in claim 7, wherein the pile is a metal conduit having an outside diameter of about 42 inches and a wall thickness of about 1 1/2 inches.
 13. An assembly, as set forth in claim 7, including a metal jacket positioned about the pile and extending from a location above the body of water, through the body of water and into contact with the first formation. 